The incident took place in the vicinity of the restive Marjah district after a civilian vehicle crossing the area struck with an improvised explosive device planted by the militants.
A security official said at least seven civilians were and three others were wounded in the explosion.
Helmand is among the relatively volatile provinces in south of Afghanistan where the anti-government armed militant groups actively operate in its various districts.
However, no individual or group has so far claimed responsibility behind the incident.
The anti-government armed militant groups frequently use explosives materials for the roadside bombings and car bombings to target the government staff and security personnel.
However, in majority of such incidents the ordinary civilians are targeted besides such bombings incur casualties to the security personnel.
In some cases the tactic also prove deadly for the militants as occasionally reports emerge regarding the premature explosions among the Taliban militants and other insurgents who are attempting to manufacture or plant IEDS on the roadsides.